In a transfer machine for performing, at special stations, a number of operations on a work part, the part is usually carried by the pallet from the station. The pallet is precisely positioned at a particular station and clamped while the particular operation on the workpiece is carried out, whether it be milling or drilling, etc. Sometimes a "soft" clamp is used for the pallets, namely, a clamp which is opened mechanically and closed with a spring. Other instances include a "hard" clamp wherein the clamp is possibly opened by a spring but closed with a mechanical motion or hydraulically. The pallet usually slides on transfer rails extending through the machine.
The work part must also be clamped on the pallet. Since the parts are sometimes quite heavy and must be well secured, heavy clamping pressures are applied. One of the problems which has arisen in the art is the uneven wearing of the transfer rails at edge portions. I have discovered that part of this undesirable wear has resulted from distortion of the pallets by the clamping pressure. The tighter the clamp, the greater the distortion and the greater the line or spot wear on the transfer rails.